String regEx =   "^(([//w-]+//.)+[//w-]+|([a-zA-Z]{1}|[//w-]{2,}))@"     +"((([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])//.([0-1]?"     +"[0-9]{1,2}|25[0-5]|2[0-4][0-9])//."     +"([0-1]?[0-9]{1,2}|25[0-5]|2[0-4][0-9])//.([0-1]?"     +"[0-9]{1,2}|25[0-5]|2[0-4][0-9])){1}|"     +"([a-zA-Z]+[//w-]+//.)+[a-zA-Z]{2,4})$";    public void btnValidateEmailAddress(View v)   {   strEmailAddress = editTextEmail.getText().toString().trim();      Matcher matcherObj = Pattern.compile(regEx).matcher(strEmailAddress);      if (matcherObj.matches())     {     Toast.makeText(v.getContext(), strEmailAddress+" is valid", Toast.LENGTH_SHORT).show();     }     else     {     Toast.makeText(v.getContext(), strEmailAddress+" is InValid", Toast.LENGTH_SHORT).show();     }   }